Field of the Invention
The present invention relates to an image-forming apparatus such as an electrophotographic printer.
Description of the Related Art
In many image-forming apparatuses to which an option unit, such as a sheet discharging unit, can be connected, a power supply plug of the option unit is connected to the image-forming apparatus so that the image-forming apparatus can supply power to the option unit. In such an apparatus form, the total current consumed by the image-forming apparatus and the option unit needs to be equal to or smaller than the rated current consumption of a commercial power supply, 15 A.
Some option units operate in a plurality of operation modes with different current consumptions. An image-forming apparatus using an electrophotographic technique has a fixing section that heats and fixes toner to a recording material. Thus, when the option unit operates in an operation mode with a large current consumption, the maximum value of the amount of current consumed by the fixing section needs to be limited compared to when the option unit operates in an operation mode with a small current consumption. For example, power consumption may be reduced by controllably turning off the fixing section while the option unit is in operation (Japanese Patent Application Laid-open No. 2004-294855). Furthermore, when the option unit operates in an operation mode with a large current consumption, sheets may be conveyed at wider sheet intervals than those in an operation mode with a small current consumption in order to gain a longer time to recover the temperature of the fixing section.
The image-forming apparatus may consecutively form images on a plurality of sheets, and during such an operation, the operation modes of the option unit may be switched over. For example, when the operation mode is switched from a mode with a large current consumption to a mode with a small current consumption, it is inefficient to continue image formation at increased sheet intervals.